Spiral balance

Thanks for contacting us! Typically, the best way to determine what spiral balance length you need is to measure the outer tube by itself. You don't want to count the inner spiral rod or anything else, just the outer tube. 

If you're still not sure, you can show us some photos of your window sashes and balances and we can try to figure out what you have. If you give us the total height and weight of the sash, as well as the visible glass height, we can do some math to calculate the proper size.